A sensor, which can be placed in a testing device in the same manner as a sample carrier and exposed to radiation from lamps, is known from sales leaflet D 310 608/2 C5.82/N Ku of the Original Hanau division of the W. C. Heraeus GmbH firm. This sensor is powered by batteries and converts the radiation of a predetermined specific spectral range into corresponding electrical signals and stores away the radiation dose. Upon completion of the test, one can display the desired values by means of a measuring device to be connected to the sensor.